Field of the Invention
The invention relates to an automatic release device for automatically releasing the setting of hold-on of a first telephone holding an outside line call from a second telephone by means of "hook-down" of the second telephone (replacement of the telephone receiver on its cradle), and also to a transfer method for transferring an outside line call received from a second telephone by a first telephone to any other lines by use of the hold-on setting automatic release device together with a "conference call" system (in which a plurality of persons can talk together using the same and single line) served by a Telegraph and Telephone Corporation.
A hold-on setting device for setting a first telephone to the hold-on state holding an outside line call from a second telephone has been provided for various telephone sets or users telephone exchange apparatuses (called "business main exchange" in Japan) and is used when the first telephone is to be temporarily off with the outside line call being kept alive, causing the transmitting person (the second telephone) to hold on the line while an aimed speaker is gotten or the call is transferred to any other lines. The hold-on setting device is operated at the call-receiving side, usually by the receiving person (the person first picked up the telephone receiver of the first telephone) through his depressing the hold-on setting button on the telephone or other manners and may be released from the hold-on setting state at the call-receiving side.
The conventional type of outside line call hold-on setting device is operated of the hold-on setting and its release only by the telephone at the call-receiving side. Release of the hold-on setting is forgettable after the hold-on setting is kept for hours, for example, when the receiving person takes time in getting the aimed speaker after setting the telephone to the hold-on state or such aimed speaker inadvertently fails to be on the line. The transmitting person has to merely hold on the line, having nothing to do in this case and will often hang up after kept waiting long, leading to the problem that the telephone at the call-receiving side is kept in the hold-on set state and cannot use the outside line on which the call has been off.
Another case having the problem that the hold-on setting on the telephone at the receiving side is not released but kept to thereby cause the line to be kept unusable is seen under such circumstance that an outside line call is transferred to any other lines by use of the conference call system served by Telegraph and Telephone Corporations, for example, Trio-phone service by Nippon Telegraph and Telephone Corp., Japan, (telephoning function that three persons can talk together using the same and single line). In this case, a call-receiving person receives an outside line call from a transmitting person, calls up a third person (to whom the outside line call is to be transferred) to establish a three persons call and then set the call-receiving person's telephone to the hold-on state, thereby allowing that transmitting person and the third person (the one to whom the outside line call is to be transferred) to talk with each other. In the above case of transferring the outside line call by use of the conference call system, when the call between that transmitting person and that third person ends, the hold-on setting on the telephone at the call-receiving person is not released but kept to thereby cause the line to be kept unusable.
Also, when the call-receiving person (the subscriber for the Trio-Phone service) merely replaces the telephone receiver on the cradle (the usual hanging up state), all the telephone communication above is broken. The call-receiving person necessarily needs to have the hold-on setting or keep "on" the telephone by picking up the telephone receiver for the purpose of providing the transfer as abovesaid. But, in the former (by the hold-on setting), hold-on tones hinders the call between that transmitting person and that third person, and in the latter, the telephone receiver picked up is a bother and does not keep secret any confidential conversation between those persons. Hence, the trio-phone service may be usable only for the three-persons call but is practically unreasonable to be applied for the aforesaid transfer of outside line call.